23 Mar 2008

Knee under MRI scanner

As promised, I am back, enriched with the experience of being under an MRI scanner.

MRI or Multiple Resonance Imaging is a relatively recent development in medical scan devices. Though costlier than the other options, it is prefered because of the high level of detail achieved and also because there is no radiation involved which makes it safer than X-Rays and CT scans. There are complex principles of physics and maths in the background; nevertheless we can make an attempt to understand how an MRI works in simple terms.

Our body has water. Water is composed of hydrogen and oxygen. The nucleus of hydrogen is nothing but a proton.

First the scanner produces a strong magnetic field bringing all such protons to a state of alignment like a platoon of soldiers under command by a general. Next, the protons are showered with radio waves Many of the protons absorb the radio waves and lose alignment with the magnetic field. It's like circulating a boxes of chocolates through the platoon at attention. Some of the soldiers will run after the chocolates. But soon the magnetic field general growls order order and the errant protons snap back to their erstwhile positions. The cycle repeats. This falling out of alignment and snapping back produces a magnetic signal which can be tapped and mapped into an image.

The MRI section is two floors below the ground. We were late by about twenty minutes, thanks to Bangalore traffic, and I had to wait for about an hour to get another MRI slot. The lady behind the counter said MRI gets over in half an hour if the patient cooperates. One has to keep still, without a movement of the area under scan. I guess the person who went in before me did not realize this.

When my turn came, the attenders ushered me into a changing room with a pair of hospital clothes -- shirt and pajama with purple stripes. I chanced to bump into a radiologist and he told me I needn't change as far as whatever I was wearing had no metallic component. The magnet of the scanner is powerful enough to pull out anything metallic and it could ruin the scan. In fact if there are metal implants inside the body, MRI is not advised.

They made me lie down on a stretcher with a support bracket for the right knee. The arms of the bracket converged to hold the knee in place. Soon I was facing the long, deep tube of the scanner with an opening like a front loading washing machine door. The stretcher went in slowly, feet first, till only my head was outside and I could just read the buttons and symbols on the scanner.

One of the doctors had put a headphone over my ears to mute the machine noises during the scan with film music. I did not have to wait long to appreciate the step. The scanner roared and thudded for half an hour like a jet taking off and if it hadn't been for the headphone, I would have gone deaf. I watched the lightning bolt symbol (like Harry Potter's) on the machine glow on and off and other readings change though I couldn't make out much. All the while, as instructed by the doctor I kept my leg still. It was difficult with the racy music though. Chaiyan chaiyan from Dil Se is beaty enough to make a corpse get up and start jigging. So is muqabla muqabla featuring the boneless Prabhu Deva. It was hard but I managed to keep a still leg and cooperate; the scan got over in twenty five minutes, though I would have to wait for a couple of days before the processing of image and preparation of report.

The scan happened on Thursday. I visited the doctor on Saturday with the MRI report and strips upon strips of negative like images of the knee, in four sheets.

Good news! There is no damage to the ligament and hence no immediate need of any surgery. The meniscus has a tear which should heal naturally. I can resume normal life though without stressing the knee too much. I need to walk and climb steps slowly and wear a knee cap while going out. There is a simple raising-and-lowering-the-leg exercise to be done daily. However no running and no playing :-( till one month at the end of which Dr. Ramanna will examine the knee again.

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